https://github.com/scala/docs.scala-lang/blob/1ae6d880f8a2298ab5150e88740ce5672b16a89a/_overviews/core/futures.md?plain=1#L1184 It should be like: ``` completion match { case Failure(exception) if exception.getCause != null => println(s" caused by ${exception.getCause}") case _ => () }